The barrage structure includes a boat
lock,
spillway,
fish pass and
generator turbine. The turbine serves a dual use: acting as a power generator for the
National Grid as well as being used to pump water back into the Tawe River system. The barrage has an installed generating capacity of . The barrage scheme gave rise to a number of environmental concerns.
Fish navigation up the river and
dissolved oxygen levels were problems that arose after completion.
Salt water that came in at high spring tides sank to the bottom and stayed there as it is denser than fresh water, reducing oxygen levels for fish. The
Environmental Advice Centre was commissioned to undertake an
aeration scheme trial in the Tawe in the summer of 1998. The system was based on a diffuser design and propeller mixer, which proved highly effective at exporting the salt water from the deep area of the trial site and raising dissolved oxygen concentrations at the bed. Following the success of the trial system, a more extensive system was designed for installation in 1999–2000. The installation was conducted using a diving team to ensure optimal location of the diffusers within the river channel. The installation was expected to treat all the problem areas over a long reach of river and ameliorate the poor
water quality present in these areas. Monitoring results from the system installed to date have indicated that aeration has effectively raised the oxygen concentration and assisted in the export of saline water from the system. Other fears that arose with the building of the barrage such as the raising of the
water table causing ground
subsidence problems in the low-lying areas around the River Tawe did not materialize. == Similar projects ==